The routing entity recieves upcalls from the network entity with packets that
require next-hop information. It also receives upcalls that allow it to peek
at all packets that arrive at a node. It sends downcalls to the network entity
with next-hop information when it becomes available. SWANS implements the
Zone Routing Protocol (ZRP) [3], Dynamic Source Routing (DSR)
[4] and ad hoc On-demand Distance Vector Routing (AODV)
[7].